Embodiments relate to detection of anomalies and, more particularly, to use of infrared filters for detection of anomalies in a scene while stationary and/or on-the-move.
Deployed troops can be endangered by improvised explosive devices (IEDs). Most IEDs have some element (ordnance, pressure plates, wires, etc.) on the surface, near-surface or deeply buried in the ground and/or ground disturbance resulting from human or mechanical emplacement activity. The current state of the art (SOA) of detection systems for sensing disturbed ground include laser spectroscopy, broadband imaging and hyperspectral imaging over the visible and infrared spectrum.
The emissivity signature of silicates in soil, known as the Reststrahlen effect, is found in the long wave infrared (LWIR) spectrum, roughly between 8.2 μm and 9.4 μm. As known in the art, the emissivity of a material (usually written ε or e) is the relative ability of the surface of the material to emit energy by radiation, and is expressed as the ratio of energy radiated by the material to the energy that would be radiated by an ideal black body at the same temperature. Use of a LWIR hyperspectral approach is one known method used to detect spectral phenomena associated with the Reststrahlen effect. While the hyperspectral approach is capable of capturing the Reststrahlen signature, it is not optimum for providing thorough integrated thermal imagery that is important to situational awareness and the discovery of local thermal variations due to surface and near-surface emplacements and changes in soil character, density and moisture related to deeper buried articles. A hyperspectral approach may also be susceptible to impacts from shifts in the spectral content due to unique character of the soils. These limitations are due, in part, to the narrow bandwidth involved with the hyperspectral approach which has a low signal-to-noise ratio (“SNR”).